SEPTUM, HIPPOCAMPUS, PALLIAL COMMISSURES 393 



into the ventricle as a transverse ridge. Just lateral to the 

 attachment of the tela is the fimbrio-dentate sulcus. Above the 

 fascia dentata the deep fissura hippocampi presents the typical 

 mammalian relations. The constitution of the anterior pallial 

 commissure is discussed in a later section. 



In the bat (fig. 44) the section cuts the two commissures very 

 much as in the opossum. Above the anterior pallial commissure 

 is a well developed hippocampus and fascia dentata. The hip- 

 pocampal fissure and the fimbrio-dentate sulcus are similar to 

 those of Didelphys. The lateral ventricles are reduced to very 

 narrow slits. The medial wall of the ventricle consists of a pri- 

 mordium hippocampi in which the pallial commissure is im- 

 bedded as in all other forms. 



In the mole (fig. 51) the section cuts the large anterior com- 

 missure, the fornix columns and the corpus callosum. Above 

 the corpus callosum is the indusium with the stria Lancisii, and 

 beneath it the primordium hippocampi which is relatively larger 

 than in any other mammalian brain studied. Between the for- 

 nix columns it contains large cells comparable with the large 

 pyramids of the hippocampus. The relations of the neuroporic 

 recess are commented upon in connection with the sagittal sec- 

 tion, which shows them better. 



In the rabbit (figs. 69, 70) the general relations are the same 

 as in the mole. A very small indusium appears above the corpus 

 callosum. The septum pellucidum of authors consists of a dif- 

 fuse gray mass which is directly continuous forward with the 

 primordium hippocampi. Just rostral to the neuroporic recess 

 each lateral half of this primordium is almost semicircular in 

 outline (fig. 69). The fornix columns come up through it, a 

 large part of their fibers turning laterad as the body of the fornix 

 to become continuous with the fimbria, another large part ascend- 

 ing to take a place immediately beneath the corpus callosum 

 near the median line in which position the fibers continue caudad 

 to be distributed to the hippocampus. This is the fornix supe- 

 rior of KoUiker and Elliot Smith. The fornix body divides at 

 the level of the neuroporic recess into dorsal and ventral por- 

 tions. The dorsal portion forms a thin covering for that part 



